Press mold for glass substrate

ABSTRACT

A press mold for glass substrate includes an upper mold and a lower mold, and a pressure apparatus for applying pressure to the upper mold and the lower mold, for molding a plate-shaped glass substrate having a predetermined thickness between the upper mold and the lower mold. An engaging projected piece is projectingly provided on the side portion of the upper mold, an engaging projected piece supporting portion for supporting the engaging projected piece is provided on the side portion of the lower mold, and an end portion of the upper mold is formed so as to be released from the lower mold with the engaging projected piece as a rotating shaft. Variance in pressure on mold surfaces between the upper mold and lower mold is detected, and a buffer made of material having lower compressive yield strength than material constituting the lower mold is inserted between the lower mold and the pressure apparatus in a position corresponding to the mold surface portion at lower pressure. It is possible to prevent the molded object or the mold from being damaged, and to apply uniform pressure on an entire mold surface by eliminating pressure variance on the mold surface of the mold as far as possible, and therefore, a large glass substrate molded object of excellent quality can be molded.

BACKGROUND OF THE INVENTION AND RELATED ART

The present invention relates to a press mold for press molding a largeplate-shaped glass substrate molded object, and a pressing method forthe glass substrate.

As fiber alignment components, there are known fiber arrays which areused to connect fibers with other optical components, and MT connectorswhich are used to connect fibers with one another. These connectingoptical components are fabricated using a glass substrate having fibersecuring grooves. The molded object for a glass substrate having suchgrooves on its surface is generally molded using a press mold consistingof an upper mold and a lower mold.

That is, the glass substrate is fabricated by flowing molten glassmaterial into a mold for press molding. In press molding for aplate-shaped glass substrate, the glass substrate is normally fabricatedby means of a two-step molding process consisting of a first step ofmolding from molten glass to a plate-shaped glass substrate, and asecond step of molding more precisely by re-heating the glass substrateobtained in the first step.

Here, in the case of molding a glass substrate having grooves on itssurface as described above, in the second step, a so-called re-heatpress process, molding is performed using a press mold consisting of anupper mold and a lower mold each having a groove-shaped mold surface. Inrecent years, a large glass substrate molded object has been requestedin terms of operation efficiency and cost.

If, however, the glass substrate molded object is made as large as, forexample, two inches or more in diameter, a tensile force of a fixedvalue or more is exerted between the molds and the glass substratemolded object when the mold is released after pressing, and as a result,the glass substrate molded object and the molds may be damaged. Also,when the glass substrate size is made larger and the thickness is madethinner, the tensile force tends to become larger.

The present invention has been achieved in the light of above-describedconventional problem, and is aimed to provide a press mold for glasssubstrate and a pressing method capable of applying uniform pressure toan entire mold surface and thereby preventing a molded object or a moldfrom being damaged and eliminating variance in pressure on the moldsurface of the mold as far as possible on molding a large glasssubstrate molded object.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a press mold for aglass substrate comprising an upper mold and a lower mold, and pressuremeans for applying pressure to the upper mold and the lower mold, formolding a plate-shaped glass substrate having a predetermined thicknessbetween the upper mold and the lower mold, wherein an engaging projectedpiece is projectingly provided on a side portion of the foregoing uppermold, an engaging projected piece supporting portion for supporting theengaging projected piece is provided on a side portion of the foregoinglower mold, and the end portion of the upper mold is formed so as to bereleased from the lower mold with the engaging projected piece as arotating shaft.

Also, in the present invention, it is preferable that there is arrangeda pressure member above the upper mold with a pressure intermediateplate interposed therebetween, and the central upper surface of thepressure intermediate plate is formed into a concave shape, and aspherical seat formed into such a convex shape as to correspond to theconcave shape on the pressure intermediate plate is provided on thecentral lower surface of the pressure member.

Also, according to the present invention, there is provided a pressingmethod for a glass substrate for molding a plate-shaped glass substratehaving a predetermined thickness between the upper mold and the lowermold by applying pressure to the upper mold and the lower mold throughpressure means, wherein variance in pressure on mold surfaces in theforegoing upper mold and lower mold are detected, and a buffer made ofmaterial having lower compressive yield strength than materialconstituting the lower mold is inserted between the lower mold and thepressure means in a position corresponding to a mold surface portion atlower pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional structural view showing an embodiment of apress mold for glass substrate according to the present invention;

FIGS. 2(a), (b) and (c) are side explanatory views schematicallyillustrating operations of a press mold according to the presentinvention, and FIG. 2(a), FIG. 2(b) and FIG. 2(c) show states beforepressing, during pressing and during mold release after pressing,respectively;

FIGS. 3(a), (b) and (c) are side explanatory views schematicallyillustrating a retracting operation of an upper mold according to thepresent invention, and FIG. 3(a), FIG. 3(b) and FIG. 3(c) show statesimmediately after pressing, at the beginning of mold release and whenthe upper mold leaves the glass material, respectively;

FIG. 4 is a partial enlarged view for FIG. 3(b); and

FIG. 5 is a cross-sectional view showing another example of an engagingprojected piece supporting portion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, with reference to the drawings, the detailed descriptionwill be made of an embodiment according to the present invention.

FIG. 1 is a cross-sectional structural view showing an embodiment of apress mold for glass substrate according to the present invention.

In FIG. 1, a press mold 10 has an upper mold 11, a lower mold 12, andpressure shafts 13, 14 of pressure means for applying pressure to theupper mold 11 and the lower mold 12. Above the upper mold 11, there isprovided a pressure member 16 with a pressure intermediate plate 15interposed therebetween, and the pressure member 16 is coupled to theforegoing pressure shaft 13. The pressure intermediate plate 15 has aconcave portion 17 formed on the central upper surface thereof, and aconvex portion of a spherical seat 18 provided on the central lowersurface of the pressure member 16 is engaged with the concave portion17.

Even if there is any deviation in parallelism between the upper mold 11and the lower mold 12, the above-described structure allows a fittedportion between the concave portion 17 on the pressure intermediateplate 15 and the convex portion of the spherical seat 18 to absorb thedeviation, thus preventing the thickness of the glass substrate frombecoming uneven.

In this respect, when a taper-shaped coupling member 28 is providedunder the lower mold 12 with the lower surface plate 19 interposedtherebetween, even if there is any strain resulting from the lower mold12 and the lower surface plate 19 having inferior flatness/parallelism,this strain can be absorbed, and therefore it is preferable to providethe taper-shaped coupling member 28.

Also, in the upper mold 11 according to the present invention, anengaging projected piece 20 is projectingly provided on the side portionthereof, and, on the side portion of the lower mold 12, there isprovided an engaging projected piece supporting portion 21 which doesnot fix, but supports the engaging projected piece 20 of the upper mold11 from below and the side portion thereof. Thus, during mold releaseafter pressing, the end portion of the upper mold 11 on the other sideof the engaging projected piece 20 is caused to be released from thelower mold 12 with the engaging projected piece 20 as a rotating shaft.

Hereinafter, with reference to FIGS. 2(a), (b) and (c), FIGS. 3(a), (b)and (c), and FIG. 4, the description will be made of the structure ofthe upper mold and lower mold, and the operation of the upper mold andlower mold during pressing and during mold release.

FIG. 2(a) shows a state before pressing, and a plate-shaped glassmaterial 22 is arranged between the upper mold 11 and the lower mold 12.In this state, as shown in FIG. 4, the distal end of the engagingprojected piece 20 is in contact with the side portion 24 of theengaging projected piece supporting portion 21, but the lower portion 26of the engaging projected piece 20 is not in contact with the base 25 ofthe engaging projected piece supporting portion 21. Also, the engagingprojected piece 20 is not fixed to the engaging projected piecesupporting portion 21.

In this state, the upper mold 11 and the lower mold 12 are pressed fromabove and from below as shown in FIG. 2(b) to make a multiplicity ofgrooves on the surfaces of a molded object for glass substrate.

After the pressing is terminated, the upper mold 11 is lifted upward(retracted) as shown in FIG. 2(c) to thereby mold release, and theoperation of the upper mold during the mold release will be describedwith reference to FIGS. 3(a), (b) and (c) and FIG. 4.

FIG. 3(a) shows a state when the pressing is terminated, and next, theend portion of the upper mold 11 on the other side of the engagingprojected piece 20 is lifted upward with the engaging projected piece 20as the rotating shaft as shown in FIG. 3(b) to release from the lowermold 12. At this time, as shown in the enlarged view of FIG. 4, therotating shaft of the upper mold 11 is a lower edge portion 23 of theside portion of the upper mold 11 at the beginning of the mold release,and as the end portion of the upper mold 11 on the other side of theengaging projected piece 20 lifts upward, the lower edge portion 23 ofthe side portion of the upper mold 11, which is the rotating shaft,moves to the right in, as shown the figure, while it is sliding on theupper surface of the glass material 22. At this time, the lower edgeportion 23 of the side portion of the upper mold 11 does not leave theupper surface of the glass material 22.

Next, as the end portion of the upper mold 11 on the other side of theengaging projected piece 20 lifts upward, the distal end portion of theengaging projected piece 20 abuts the base 25 of the engaging projectedpiece supporting portion 21 and ceases the downward movement while it issliding downward in contact with the side portion 24 of the engagingprojected piece supporting portion 21.

When the end portion of the upper mold 11 on the other side of theengaging projected piece 20 further lifts upward in a state in which thedistal end portion of the engaging projected piece 20 cannot movedownward and sideways by the side portion 24 and the base 25 of theengaging projected piece supporting portion 21, a distal end portion Aof the engaging projected piece 20 serves as the rotating shaft and theupper mold 11 lifts upward. Therefore the lower edge portion 23 of theside portion of the upper mold 11 also leaves the upper surface of theglass material 22 at this time.

In a press mold according to the present invention, since the upper moldis not lifted upward in the vertical direction in this way, but from oneend portion during mold release, little or no tensile force is exertedbetween the upper and lower molds and the glass substrate molded object.Therefore, it is possible to mold release while preventing the moldedobject or the mold from being damaged. Also, during mold release, andparticularly at the beginning of the mold release the upper mold 11operates, such that, the lower edge portion 23 of the side portion ofthe upper mold 11 moves to the right in the figure while it is slidingon the upper surface of the glass material 22, and therefore, the moldrelease characteristics are improved.

In this respect, the direction of grooves formed on the surface of theglass material 22 is preferably in a mold release direction, that is,parallel to a line (direction) connecting the engaging projected piece20 of the upper mold 11 with the end portion on the other side thereof,in terms of preventing the glass substrate molded object or the moldfrom being damaged. Further, this is also preferable in terms ofimprovement in mold release characteristics.

Also, a corner portion 29 ranging from the side portion 24 to the base25 of the engaging projected piece supporting portion 21 is preferablyformed in a radius (R) shape as shown in FIG. 5 in order to smoothlyretract the upper mold 11.

Further, in the present invention, air is blown between the upper moldand the lower mold after press molding, in order to improve the moldrelease characteristics. Therefore, it is preferable to adopt the pressmold structure according to the present invention and to also performthis blowing of air. In addition, the blowing of air operates to coolthe mold, resulting in a shortened cycle time of the re-heat press.

This air blowing method is normally performed from the side of the mold,and its effect may be increased by blowing air from all four directionsof the mold. In this respect, even if air is blown from one direction ofthe mold, the effect can be exhibited as a matter of course.

The description will be made of the pressing method according to thepresent invention.

As shown in FIG. 1, through the pressure shaft 13 of the pressure means,the pressure member 16 and the pressure intermediate plate 15 withrespect to the upper mold 11, and through the pressure shaft 14 of thepressure means, the coupling member 28 and the lower surface plate 19with respect to the lower mold 12, mold clamping pressure is appliedfrom the upper limit direction to press mold a plate-shaped glasssubstrate having a predetermined thickness between the upper mold 11 andthe lower mold 12.

When, however, the glass substrate molded object becomes larger, themold also becomes larger as an inevitable consequence, and the pressureto be applied to the entire mold is increased. When the pressure appliedto the entire mold is thus increased, variance occurs in the pressureapplied onto the mold surface between the upper mold 11 and the lowermold 12. Variance in pressure causes variance in the moldability withinthe mold, thus adversely affecting the quality of the glass substratemolded object.

Thus, according to the present invention, pressure variance on the moldsurfaces between the upper mold 11 and the lower mold 12 is detected,and a buffer 30 is inserted and arranged between the lower mold 12 andthe lower surface plate 19 in a position corresponding to the moldsurface portion at lower pressure to uniformize the mold clampingpressure.

As the buffer used in the present invention, there is used one made ofmaterial having lower compressive yield strength than the materialconstituting the lower mold.

That is, when press pressure is applied to the upper and lower molds,compressive stress is exerted on each of the buffer 30, the upper mold11 and the lower mold 12. At this time, since the buffer 30 has lowercompressive yield strength than the material constituting the lower mold12, the buffer 30 is crushed earlier than the lower mold 12 to absorbthe compressive strain, and prevents the mold from being deformed. Thepressure is uniformly applied to the entire mold surface of the mold,thus making it possible to obtain an excellent quality of plate-shapedglass substrate molded object.

As the material for the buffer, one made of material which is moreflexible than the mold or materials used for the surrounding members andwhich is difficult to change depending on temperature is suitable.Generally, heat resisting steel, ultra high strength steel or the likeis used for the mold material, and concretely a stainless steel (SUS)system of members are preferable.

As the shape of the buffer, a stitch type plate which loses its shape inproportion to pressure applied, or a narrow strap-shaped plate ispreferable, and this is preferably interposed between the lower mold 12and the lower surface plate 19 or between the lower surface plate 19 andthe coupling member 28.

As described above, according to a press mold and a pressing method ofthe present invention, it is possible to prevent a molded object or amold from being damaged during mold release, and to apply uniformpressure on the entire mold surface by eliminating pressure variance ona mold surface of the mold as far as possible, and therefore, a largeglass substrate molded object of excellent quality can be molded.

What is claimed is:
 1. A press mold for a glass substrate, comprising anupper mold and a lower mold, and a pressure means for applying pressureto said upper mold and said lower mold, wherein said pressure meansenables molding of a plate shaped glass substrate having a predeterminedthickness between said upper mold and said lower mold, wherein anengaging projected piece is projectingly provided on a side portion ofsaid upper mold, an engaging projected piece supporting portion forsupporting said engaging projected piece is provided on a side portionof said lower mold, and an end portion of said upper mold is formed soas to be released from said lower mold with said engaging projectedpiece serving as a rotating shaft, wherein said engaging projected piecesupporting portion does not fix the engaging projected piece.
 2. Thepress mold for glass substrate according to claim 1, wherein saidpressure member is arranged above said upper mold with a pressureintermediate plate interposed therebetween, and a central upper surfaceof said pressure intermediate plate is formed into a concave shape, anda spherical seat formed into such a convex shape as to correspond to theconcave shape in said pressure intermediate plate is provided on acentral lower surface of said pressure member.
 3. The press mold forglass substrate according to claim 1, further comprising means forblowing air between said upper mold and said lower mold, on the side ofsaid mold, which blows air between said upper mold and said lower moldafter press molding.